1. Field of the Invention
The present invention relates to a panel for a cathode ray tube and, more particularly, to a flat panel for a cathode ray tube in which external light reflection is minimized, appearance is improved, natural view of screen images is possible, and to which a shadow mask may be applied.
2. Description of the Related Art
In general, a cathode ray tube includes a phosphor screen applied with three colors, red, green and blue, a shadow mask for selecting colors, an electron gun for emitting electron beams, and a deflection yoke for deflecting the electron beams on the phosphor screen, wherein the electron beams for the three colors, red, green and blue, reach respective phosphor substances passing through apertures formed on the shadow mask to form desired images on a front panel of the cathode ray tube.
The phosphor screen coated with the phosphor substances is provided on an inner surface of a panel forming a body part of the cathode ray tube with a funnel, wherein the panel is usually formed with a curved inner surface and a curved outer surface using a transparent glass plate.
Such prior art panels, however, have limitations in terms of undesirable reflection of external light and distortion of the screen image as the outer surface is not flat. The current trend, therefore, is to move towards a flat panel wherein an outer surface is formed flat.
As shown in FIG. 3, such a flat panel employs typically a panel 30, of which both the inner and outer surfaces 31, 32 are formed flat, and a flat tension mask 33 having good tension force in both the horizontal and vertical directions for minimizing the degradation of screen quality due to a so-called “doming” phenomenon.
Further, a panel, of which an outer surface is formed flat and an inner surface has a curvature only in the horizontal direction, is utilized, wherein the panel employs an aperture grill which is applied with a tension force in the vertical direction in consideration of the the flat inner surface.
FIG. 4 shows a screen image 35 displayed to a user U at a distance apart from the flat panel 30, the distance being a function of the width of a screen. In FIG. 4, the screen image 35 which is substantially realized on an inner surface 32 of the flat panel 30 along sight or eye line E is refracted while passing through the outer surface and is seen by the user U as if the screen image is positioned between the outer surface 31 and the inner surface 32 of the panel 30.
Such a conventional flat panel 30, however, has a disadvantage in that a natural screen image may not be realized due to a screen distortion phenomenon wherein the screen image appears to be concave inwardly as the size of the panel increases due to the refraction of the screen image along the sight or eye line as it passes through the flat panel 30.
Further, the color selection function becomes limited to the flat tension mask or the aperture grill forming a mask surface by the tension force, so that it is impossible to compatibly use the flat panel in an existing cathode ray tube having a shadow mask.